We have demonstrated the efficacy of microwave discharge activation of tritium gas in obtaining high specific activity H3 adrenocorticotropin with full biologic activity. During the next three years, we propose: 1) To describe the chemistry of this reaction with protein primary constituents by studying the labeling characteristics of a series of biologically active peptides of known structure; 2) To study the effect of secondary, tertiary and quaternary structure upon the labeling of primary constituents; 3) To study the effect of the reaction upon structure-function relations of specific proteins; 4) To establish the minimum criteria required to demonstrate radiochemical homogeneity; and 5) To design, in collaboration with other investigators, biochemical and physiologic systems in which the utility of these labeled molecules can be validated. If successful, these studies will extend tritium labeling techniques and tracer methodology to peptide and protein biochemistry and physiology, thereby opening up new avenues of approach to research in many fields previously inaccessible. This work is part of an ongoing collaboration between our laboratories and those Dr. Alfred P. Wolf in the Department of Chemistry at the Brookhaven National Laboratories. Facilities available in both institutions permit us to draw upon the experience and skills of both and to conduct all labeling experiments in three phases, facilitating rapid purification and minimizing contamination. Our experience gained in the development of this tritium labeling methods and our combined interests and skills in organic chemistry and biochemistry put us in the unique position of having the greatest possible change of demonstrating that this method can be use generally to prepare tritiated peptide and protein hormones.